KR20050085822A - Self-adhesive article comprising at least one layer made from a thermally-conducting adhesive mass and method for production thereof - Google Patents

Abstract

In a method for production of a self-adhesive article a thermally- conducting adhesive mass containing acrylate is coated on a support in a hot-melt coating method with stretching or orientation such that an anisotropic thermally-conducting layer with a back-shrinkage of at least 3 % measured on the free adhesive mass film is generated.

Description

Self-adhesive article having at least one layer made of a thermally conductive adhesive material and a method for manufacturing the same. {SELF-ADHESIVE ARTICLE COMPRISING AT LEAST LAYER MADE FROM A THERMALLY-CONDUCTING ADHESIVE MASS AND METHOD FOR PRODUCTION THEREOF}

The present invention provides a method for producing a pressure sensitive adhesive article having at least one layer made of a thermally conductive pressure sensitive adhesive (PSA) material and also a pressure reduction obtainable in this way for adhesive bonding, particularly in the field of electrical and electronic components. Relates to a sex adhesive article.

In the computerized era, electronic components must be increasingly processed and adhesively bonded to each other. As a result of miniaturization, the requirements imposed on pressure sensitive adhesives are also becoming more stringent. For example, very high temperatures can often occur in electronic circuits and this heat must be removed. For this application, for example, elements providing active cooling are combined. To ensure effective heat transfer, the adhesive material must exhibit very good thermal conductivity. Moreover, the corresponding pressure sensitive adhesives must be suitable for use at a wide range of temperatures, exhibit low outgassing and be very stable against aging. Acrylate PSA meets the latter requirement very well.

U. S. Patent No. 4,722, 960 mixes acrylate with aluminum particles and free radical initiators and uses the mixture for adhesive bonding. However, for this method, very much time is required for adhesive bonding because the monomer mixture must be thermally crosslinked.

U. S. Patent No. 6,228, 965 describes an acrylate copolymer mixture that is in turn mixed with a thermally conductive material. In this way, it is also possible to obtain acrylate PSAs which are thermally conductive and can be used for bonding without applying high pressure.

However, as a result of the further shrinking and increasingly adjoining configurations of the individual electronic components, increasingly stringent requirements are placed on the flow behavior of the PSA. Thus, there is a need, for example, to prevent a situation in which the PSA leaks out laterally after adhesive bonding of two electronic components, causing inadequate work to connect other circuits. However, this cannot be guaranteed by, for example, the PSA described in US Pat. No. 6,228,985.

It is therefore an object of the present invention to provide thermally conductive pressure sensitive adhesives, in particular in the electrical and electronics industry, in which the disadvantages in the prior art have been avoided and, in particular, swelling or exterior of the pressure sensitive adhesive to the outside at the bonding edges. The outflow of the furnace was certainly prevented.

This object has been surprisingly achieved and in a manner unexpected to those skilled in the art, with carriers having at least 3% shrinkage recovery by means of means of anisotropy (including temporary carriers in which the pressure-sensitive adhesive can be removed again). An oriented pressure sensitive adhesive having a coating on it is obtained and an associated pressure sensitive adhesive article is obtained in this manner. New development steps of the invention are characterized in the dependent claims.

The achievement of the object of the present invention is an electrical or electronic, having at least one layer of a thermally conductive pressure sensitive adhesive, ie a pressure sensitive adhesive based on polyacrylate and / or polymethacrylate in the absence or presence of additional comonomers. A method of making a pressure sensitive adhesive article for joining a part, wherein a layer that is anisotropic for at least one property is made from a thermally conductive pressure sensitive adhesive in a coating process by stretching, drawing, or pressing, and the layer The silver has a shrinkage recoverability of at least 3% in at least one direction along the plane of the layer, as measured by shrinkage recoverability measurement in accordance with Test B on a glass film at the end of the layer.

Anisotropy means that one or more properties of the pressure-sensitive adhesive in one spatial direction in the PSA layer are different from the same properties in one or more other directions, in other words, the anisotropic property is directional and not uniform in the material.

The pressure sensitive adhesive preferably possesses a known orientation, such as a deflecting direction, in the polymer structure.

The coating process may be, for example, a hot melt roll coating process, a melt die coating process or an extrusion coating process.

In another aspect of the invention, the coating process is a conventional coating process from a solution, for example where the coating is followed by stretching or drawing on a carrier layer which is preferably stretchable.

The thermally conductive pressure sensitive adhesive may be coated by a coating process on one or both sides of a sheet or tape carrier, which may be a transfer tape or release liner. The carrier material itself may be thermally conductive in one possible embodiment.

Pressure sensitive adhesives that can be used according to the invention

Anisotropic pressure-sensitive adhesives themselves are known. They are also referred to below as anisotropically oriented or simply "oriented pressure sensitive adhesives."

Anisotropically oriented PSAs possess a tendency to revert to their initial state as a result of their 'entropy-elastic' action after stretching in a given direction.

In the present invention, as PSA, it is preferable to use (meth) acrylate PSA or polyacrylate- and / or polymethacrylate-based PSA, that is, polyacrylate and / or polymethacrylate in a significant or significant proportion. And associated derivatives.

The monomers are preferably selected such that the polymer obtained can be used as PSA at room or elevated temperature, in particular the polymer obtained is described in "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York 1989). ] In accordance with the pressure-sensitive adhesive properties.

Polymers which are preferably used as elastic thermally conductive PSAs are preferably of the formula CH ₂ = CH (R ₁ ) (COOR ₂ ) where R ₁ is H or CH ₃ and R ₂ is alkyl having 1 to 20 carbon atoms Chain or H), which can be obtained by polymerizing a monomer mixture consisting of high or significant proportions of acrylic esters and / or methacrylic esters and / or free acids.

The polyacrylate molar mass M _W used preferably amounts to at least 200,000 g / mol.

In one very preferred method, acrylic acid or methacrylic monomers are used, which consist of acrylic acid and methacrylic acid esters having 4 to 14 carbon atoms, preferably 4 to 9 alkyl groups. Without being limited to a specific enumeration, certain examples are methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n -Heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate and its side chain isomers such as isobutyl acrylic Latex, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate and isooctyl methacrylate. A further class of compounds that can be used are monofunctional acrylates and / or methacrylates of crosslinked cycloalkyl alcohols having at least 6 carbon atoms. Cycloalkyl alcohols may also be substituted, for example, with C-1-6 alkyl groups, halogen atoms or cyano groups. Specific examples are cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyladamantyl acrylate.

In one process, carboxyl radicals, sulfonic and phosphonic acids, hydroxyl radicals, lactams and lactones, N-substituted amides, N-substituted amines, carbamates, epoxies, thiols, alkoxy or cyano radicals, ethers and the like Monomers having the same polar group are used.

Suitable basic monomers are, for example, N, N-dialkyl-substituted amides such as N, N-dimethylacrylamide, N, N-dimethylmethylmethacrylamide, N-tert-butylacrylamide , N-vinylpyrrolidine, N-vinyllactam, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, N-methyllomethacrylate, N -(Butoxymethyl) methacrylamide, N-methylloacrylamide, N- (ethoxymethyl) acrylamide, N-isopropylacrylamide, and this enumeration is not limiting.

Further preferred examples are hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, allyl alcohol, maleic anhydride, itaconic anhydride, itaconic acid, glyceridyl methacrylate Phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl methacrylate, 2-butoxyethyl acrylate, cyanoethyl methacrylate, cyanoethyl acrylate, glyceryl methacrylate, 6-hydroxyhexyl methacrylate, vinylacetic acid, tetrahydrofurfuryl acrylate, β-acryloyloxypropionic acid, trichloroacrylic acid, fumaric acid, crotonic acid, aconic acid and dimethylacrylic acid, the enumeration of which is not limiting. .

In one further very preferred procedure, vinyl esters, vinyl ethers, vinyl halides, vinylidene halides and vinyl compounds having aromatic rings and heterocycles in the α-position are used as monomers. Here, non-exclusively mention may be made, for example, of vinyl acetate, vinylformamide, vinylpyridine, ethyl vinyl ether, vinyl chloride, vinylidene chloride and acrylonitrile.

In a preferred procedure, the polymerization of polymethacrylate PSA, photoinitiators with copolymerizable double bonds is used. Suitable photoinitiators include Norish I and II photoinitiators. For example, benzoin acrylate and acrylated benzophenone (manufactured by UCB (Ebecryl P 36 ^® )). In principle, it is possible to copolymerize any photoinitiators known to the person skilled in the art and capable of crosslinking the polymer by free radical mechanisms under UV irradiation. A review of possible photoinitiators that can be functional with double bonds is described in Fouassier: "Photoinitiation, Photopolymerization and Photocuring: Fundamentais and Applications", Hanser-Verlag, Munich 1995. For further supplementation see Carroy et al. in "Chemistry and Technology of UV and EB Formulations for Coatings, Inks and Paints", Oldring (ed.), 1994, SITA, London.

In another preferred procedure, the comonomers described are mixed with monomers having a high static glass transition temperature. Suitable components are styrenes which comprise aromatic vinyl compounds and for example the aromatic nucleus consists mainly of C ₄ to C ₁₈ units and may also contain heteroatoms. Particularly preferred examples are 4-vinylpyridine, N-vinylphthalimide, methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate , t-butylphenyl acrylate, t-butylphenyl methacrylate, 4-biphenylyl acrylate, 4-biphenylyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate and these monomers And mixtures thereof are not limiting.

By using the method according to the invention at least 3% shrinkage resiliency is obtained in PSA, shrinkage resiliency as measured by Test B (shrinkage resiliency measurement in glass film). In a preferred refinement, PSA with shrinkage resilience of at least 30% and very preferably at least 50% is used.

Thermally conductive PSAs used in the present invention preferably comprise the addition of a thermally conductive compound. Thus, in one preferred embodiment, a thermally conductive filler material is used. Examples of suitable filler materials include various metal particles, ceramics, aluminum oxide, aluminum nitride, titanium boride, boron nitride and silicon nitride. However, it is also possible to add all further thermally conductive materials known to those skilled in the art.

In one preferred embodiment of the invention, 5% to 200% by weight, preferably 6% to 50% by weight of the thermally conductive material is added to the pressure sensitive adhesive poly (meth) acrylate based on the weight of the PSA. And need to be ensured in all cases depending on the amount and nature of the pressure-sensitive adhesive.

The thermal conductivity of the PSA is at least 0.05 W / mk. In one preferred embodiment, the thermal conductivity is lower in the orientation direction than in the transverse or longitudinal direction.

The resin can be mixed in PSA for further improvement. As the adhesive resin to be added, any present adhesive resin and a resin described in the literature can be used without exception. Representatives that may be mentioned are pinene resins, indene resins and rosines, these disproportionated, hydrogenated, polymerized and esterified derivatives and salts, aliphatic and aromatic hydrocarbon resins, terpene resins and terpene-phenol resins and also C5, C9 and other hydrocarbon resins. Any desired combinations of these and additional resins can be used to adjust the properties of the adhesive obtained according to the requirements. Generally speaking, any resin that is compatible (soluble) with the unknown polyacrylate may be used, in particular all aliphatic, aromatic and alkylaromatic hydrocarbon resins, single monomer base hydrocarbon resins, hydrogenated hydrocarbon resins, functional hydrocarbons Resins and natural resins may be mentioned. In particular, mention may be made of those described in "Handbook of Pressurre Sensitive Adhesive Technology" by Donates Satas (Van Nostrand, 1989).

Additionally, optionally, plasticizers, additional fillers (e.g. fibers, carbon black, zinc oxide, chalk, solid or hollow glass beads, microbeads of other materials, silica, silicates), nucleating agents, expanding agents, admixtures And / or aging inhibitors may be added, for example, in the form of primary and secondary antioxidants or in the form of light stabilizers.

In an advantageous refinement of the invention, the PSA can be preferably photochemically crosslinked immediately after or during the hot melt coating, whereby the orientation state is further stabilized such that the PSA can be stabilized even during relatively long storage times under non-optimal conditions. It does not change substantially. For this purpose, a crosslinking agent and a crosslinking accelerator may be mixed. Examples of suitable crosslinking agents for electron beam crosslinking and UV crosslinking include difunctional or polyfunctional acrylates, difunctional or polyfunctional isocyanates (including blocked forms), and difunctional or multifunctional epoxides.

For any crosslinking with UV light, a UV absorbing photoinitiator can be added to the PSA. Useful photoinitiators which are used very effectively are from benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether, substituted acetophenones such as 2,2-diethoxyacetophenone [Ciba Geigy] Marketed as Irgacure 651 ^® ], 2,2-dimethoxy-2-phenyl-1-phenylethanone, dimethoxyhydroxyacetophenone, substituted α-ketols such as 2-methoxy-2-hydride Oxypropiophenone, aromatic sulfonyl chlorides such as 2-naphthylsulfonyl chloride and photoactive oximes such as 1-phenyl-1,2-propanedione 2- (O-ethoxycarbonyl) oxime .

The photoinitiators described above and other photoinitiators that may be used, and also other photoinitiators of Norrish I or Norish II type, may contain the following radicals: benzophenone, acetophenone, benzyl, benzoin, hydroxyalkylphenone, phenyl cyclo Hexyl ketone, anthraquinone, trimethylbenzoylphosphine oxide, methylthiophenylmorpholine ketone, aminoketone, azobenzoin, thioxanthone, hexaarylbisimidazole, triazine or fluorenone, each of these radicals being one additional Substituted by one or more halogen atoms and / or one or more alkyloxy groups and / or one or more amino or hydroxy groups. Representative considerations are described in Fouassier: "Photoinitiation, Photopolymerization and Photocuring: Fundamentals and Applications", Hanser-Verlag, Munich 1995. For further details see Carroy et al. in "Chemistry and Technology of UV and EB Formulations for Coatings, Inks and Paints", Oldring (ed.), 1994, SITA, London.

Manufacturing Process for PSA of the Invention

For polymerization, the resulting polymers can be used in particular as PSAs at room temperature or at elevated temperatures, in particular in the handbook of Pressure Sensitive Adhesive Technology by Donatas Satas (van Nostrand, New York 1989). The monomers are selected to have pressure sensitive adhesive properties.

In order to achieve a preferred polymer glass transition temperature T _g of 25 ° C. or lower, monomers are selected in this manner as mentioned above, and Fox formula (E1) [TG Fox, Bull. Am. Phys, Soc. It is highly preferred to select monomer mixtures of advantageously quantitative composition in such a way as to obtain the desired T _g for the polymer according to 1 (1956) 123:

In the formula, n denotes the serial number of the monomer used, w _n is the mass fraction (% by weight) for each monomer n and T _{g, n} is the glass transition temperature of each homopolymer of monomer n at K Indicates.

It is advantageous to carry out conventional free radical polymerization to prepare poly (meth) acrylate PSAs. For polymerizations that proceed with free radicals, preference is given to using initiator systems containing further free radical initiators for polymerization, in particular free radical forming azo or peroxo initiators which are thermally decomposed. In principle, however, all conventional initiators familiar to those skilled in the art for acrylates are suitable. The production of C-centric radicals is described by Houben Weyl, Methoden der Organischen Chemie, Vol. E 19a, pp. 60-147. These methods are similarly used in the first place. Examples of free radical sources are peroxides, hydroperoxides, and azo compounds; Some non-limiting examples of typical free radical photoinitiators that may be mentioned herein include potassium peroxodisulfate, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, azodiiso Butyronitrile, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate and benzpinacol. In one very preferred embodiment, the free radical initiator used is 1,1'-azobis (cyclohexanecarbonitrile) (Vazo 88 ^™ from DuPont) or azodiisobutyronitrile (AIBN).

The thermally conductive material may be mixed into the monomer before and / or after the end of the polymerization.

The average molecular weight M _w of the PSAs formed in the free radical polymerization is very preferably chosen such that their range is from 200,000 to 4000,000 g / mol and in particular for further use as thermally conductive hot melt PSAs having anisotropic behavior, PSAs having an average molecular weight M _{W of} from 400,000 to 1,400,000 g / mol are preferred. Average molecular weights are determined by matrix aided laser desorption / ionization coupled with size exclusion chromatography (GPC) or mass spectrometer (MALDI-MS).

The polymerization can be carried out in the absence of solvent, in the presence of one or more organic solvents, in the presence of water, or in the presence of a mixture of organic solvents and water. The aim is to minimize the amount of solvent used. Suitable organic solvents include straight chain alkanes (e.g. hexane, heptane, octane, isooctane), aromatic hydrocarbons (e.g. benzene, toluene, xylene), esters (e.g. ethyl, propyl, butyl or hexyl acetate), Halogenated hydrocarbons (eg chlorobenzene), alkanols (eg methanol, ethanol, ethylene glycol, ethylene glycol monomethyl ether) and ethers (eg diethyl ether, dibutyl ether) or mixtures thereof to be. Water-miscible or hydrophilic co-solvents are added to the aqueous polymerization reactant to allow the reaction mixture to be in the form of a homogeneous phase during monomer conversion. Auxiliary solvents that can be used with the advantages of the present invention are aliphatic alcohols, glycols, ethers, glycol ethers, pyrrolidines, N-alkylpyrrolidinones, N-alkylpyrrolidones, polyethylene glycols, polypropylene glycols, amides, carrs Acids and salts thereof, esters, organic sulfides, sulfoxides, sulfones, alcohol derivatives, hydroxy ether derivatives, amino alcohols, ketones and the like and also derivatives thereof, and mixtures thereof.

Depending on the conversion and temperature the polymerization time is from 2 to 72 hours. The higher the reaction temperature that can be selected, ie the higher the thermal stability of the reaction mixture, the shorter the selected reaction time can be.

With regard to the polymerization initiation, heat introduction is essential for the thermal decomposition initiator. For these initiators, polymerization can be initiated by heating to 50-160 ° C., depending on the type of initiator.

For this preparation, it may also be advantageous to polymerize the acrylate PSA without solvent. Particularly suitable techniques for use in this case are those polymerization techniques. The polymerization is initiated by UV light but the conversion is as low as about 10-30%. The resulting polymer syrup can then be bound to, for example, a film (in the simplest case ice cubes) and then polymerized in water with a high conversion. These pellets can be used continuously as acrylic hot melt adhesives and it is particularly desirable to use film materials compatible with polyacrylates for melting operations. For this production method, a thermally conductive material can be added before or after polymerization.

Another advantageous manufacturing method for poly (meth) acrylate PSAs is anionic polymerization. In this case, the reaction medium used preferably comprises an inert solvent such as aliphatic and cycloaliphatic hydrocarbons, for example or else aromatic hydrocarbons.

In this case living polymers are generally represented by the structure P _L (A) -Me, where Me is a metal of group I, for example lithium, sodium or potassium and P _L (A) is a monomer. It is a polymer block growing from A. The molar mass of the polymer during manufacture is controlled by the ratio of initiator concentration and monomer concentration. Examples of suitable polymerization initiators include, but are not limited to, n-propyllithium, n-butyllithium, secondary-butyllithium, 2-naphthylithium, cyclohexyllithium and octylithium. In addition, initiators based on samarium complexes are known for the polymerization of acrylates (Macromolecules, 1995, 28, 7886) and can be used herein.

Also further, difunctional initiators such as 1,1,4,4-tetraphenyl-1,4-dirithiobutane or 1,1,4,4-tetraphenyl-1,4-dirithioisobutane Can be used. Co-initiators can also be used. Suitable co-initiators include lithium halides, alkali metal alkoxides and alkylaluminum compounds. In one very preferred embodiment, the ligand and co-initiator allow the acrylic monomers such as n-butyl acrylate and 2-ethylhexyl acrylate to be polymerized directly and be produced in the polymer by transesterification with the corresponding alcohol. It is chosen so that it is not necessary.

Suitable methods for preparing polyacrylate PSAs with narrow molecular weight distributions also include controlled free radical polymerization methods. In this case, preference is given to using the control reagents of the formulas (I) and (II) below for the polymerization:

Where

R and R ¹ are independently selected or identical to each other,

These are,

Branched and straight chain C ₁ to C ₁₈ alkyl radicals, C ₃ to C ₁₈ alkenyl radicals; C ₃ to C ₁₈ alkynyl radicals;

Alkoxy radicals of C ₁ to C ₁₈ ;

C ₁ to C ₁₈ alkyl radicals substituted by one or more OH groups or halogen atoms or silyl ethers; C ₃ to C ₁₈ alkynyl radicals; C ₃ to C ₁₈ alkenyl radicals;

C ₂ to C ₁₈ heteroalkyl radicals having at least one oxygen atom and / or one NR ^* group in the carbon chain, wherein R ^* is any radical (in particular an organic radical);

C ₁ -C ₁₈ alkyl radicals substituted by one or more ester groups, amine groups, carbonate groups, cyano groups, isocyano groups and / or epoxy groups and / or sulfur; C ₃ -C ₁₈ alkynyl radicals, C ₃ to C ₁₈ alkenyl radicals;

C ₃ -C ₁₂ cycloalkyl radicals;

C ₆ -C ₁₈ aryl or benzyl radicals;

-Hydrogen.

Modulating reagents of type I preferably consist of the following further restricted compounds:

Halogen atoms herein are preferably F, Cl, Br or I, more preferably Cl and Br. Alkyl, alkenyl and alkynyl radicals that are well suited for the various substituents include both straight and branched chains.

Examples of alkyl radicals having 1 to 18 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t-octyl, nonyl , Decyl, undecyl, tridecyl, tetradecyl, hexadecyl and octadecyl.

Examples of alkenyl radicals having 3 to 18 carbon atoms include propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2,4-pentadienyl, 3-methyl-2-butenyl, n-2- Octenyl, n-2-dodecenyl, isododecenyl and oleyl.

Examples of alkynyl having 3 to 18 carbon atoms are propynyl, 2-butynyl, 3-butynyl, n-2-octynyl and n-2-octadecynyl.

Examples of hydroxy-substituted alkyl radicals are hydroxypropyl, hydroxybutyl and hydroxyhexyl.

Examples of halogen-substituted alkyl radicals are dichlorobutyl, monobromobutyl and trichlorohexyl.

An example of a suitable C ₂ -C ₁₈ heteroalkyl radical having at least one oxygen atom in the carbon chain is —CH ₂ —CH ₂ —O—CH ₂ —CH ₃ .

Examples of C ₃ -C ₁₂ cycloalkyl radicals include cyclopropyl, cyclopentyl, cyclohexyl and trimethylcyclohexyl.

Examples of C ₆ -C ₁₈ aryl radicals are phenyl, naphthyl, benzyl, 4-tert-butylbenzyl and other substituted phenyls such as ethylbenzyl, toluene, xylene, mesitylene, isopropylbenzene, dichlorobenzene Or bromotoluene.

Listed above are provided only examples for each group of compounds and are not claimed as complete.

Other compounds that can be used as modulating reagents include the compounds of formulas III and IV below.

Where

R ² may be selected from the groups described above for these radicals independently of R and R ¹ .

In the case of the conventional 'RAFT' process, polymerization is generally carried out at low conversion rates in order to have a very narrow molecular weight distribution (WO 98/01478 A1). However, as a result of low conversion, high fractions of residual monomers adversely affect the technical adhesive properties, residual monomers contaminate solvent recycles in the concentrating operation and the corresponding self-adhesive tapes exhibit very high outgassing behavior. These polymers cannot be used as PSAs and in particular cannot be used as hot melt PSAs. In order to overcome the disadvantage of low conversion, in one particularly preferred procedure the polymerization is initiated two or more times.

As a further controlled free radical polymerization method, nitroxide-controlled polymerization can be carried out. For free radical stabilization in a preferred procedure, nitroxides of the formula Va or Vb are used:

Where

R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ mean independently of the following compounds or atoms:

i) halides, for example chlorine, bromine or iodine,

ii) straight, branched, cyclic and heterocyclic hydrocarbons having 1 to 20 carbon atoms which may be saturated, unsaturated or aromatic,

iii) ester-COOR ¹¹ , alkoxide-OR ¹² and / or phosphonate-PO (OR ¹³ ) ₂ , wherein R ¹¹ , R ¹² or R ¹³ means radicals from group ii).

The compounds of formula (Va) or (Vb) may also be attached to any type of polymer chain (mainly such that at least one of the radicals mentioned above constitutes a polymer chain of that type), thus synthesizing polyacrylate PSA Can be used for

More preferred are modulators for the polymerization of the following types of compounds:

2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (PROXYL), 3-carbamoyl-PROXYL, 2,2-dimethyl-4,5-cyclohexyl-PROXYL, 3-oxo-PROXYL, 3-hydroxyimine-PROXYL, 3-aminomethyl-PROXYL, 3-methoxy-PROXYL, 3-t-butyl-PROXYL, 3,4-di-t-butyl-PROXYL,

2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), 4-benzoyloxy-TEMPO, 4-methoxy-TEMPO, 4-chloro-TEMPO, 4-hydroxy-TEMPO, 4 Oxo-TEMPO, 4-amino-TEMPO, 2,2,6,6-tetraethyl-1-piperidinyloxyl, 2,2,6-trimethyl-6-ethyl-1-piperidinyloxyl,

N-tert-butyl 1-phenyl-2-methylpropyl nitroxide,

N-tert-butyl 1- (2-naphthyl) -2-methylpropyl nitroxide,

N-tert-butyl 1-diethylphosphono-2,2-dimethylpropyl nitroxide,

N-tert-butyl 1-dibenzylphosphono-2,2-dimethylpropyl nitroxide,

N- (1-phenyl-2-methylpropyl) 1-diethylphosphono-1-methylethyl nitroxide,

Di-t-butyl nitroxide,

Diphenyl nitroxide,

T-butyl t-amyl nitroxide.

A series of further polymerization methods according to another method by which PSA can be prepared can be selected in the prior art:

U.S. Patent 4,581,429 A describes controlled growth free radical polymerization using a compound of the formula R'R''N-O-Y, wherein Y is a free radical species capable of polymerizing unsaturated monomers. In general, however, the reaction has a low conversion rate. A specific problem is the polymerization of acrylates which occur only in very low yields and molar masses. WO 98/13392 A1 describes open chain alkoxyamine compounds with symmetrical substitution patterns. EP 735 052 A1 describes a process for producing thermoplastic elastomers having a narrow molar mass distribution. WO 96/24620 A1 describes a polymerization process using highly specific free radical compounds, such as phosphorus containing nitroxides based on imidazolidine. WO 98/44008 A1 describes specific nitroxyls of the morpholine, piperazinone and piperazinedione systems. DE 199 49 352 A1 describes heterocyclic alkoxyamines as regulators in controlled growth free radical polymerization. Corresponding further development of alkoxyamines or the development of corresponding free nitroxides improve the efficacy for producing polyacrylates. Hawker, paper to the National Meeting of the American Chemical Society, Spring 1997; Husemann, paper to the IUPAC World-Polymer Meeting 1998, Gold Coast.

As a further controlled polymerization method, atomic transfer radical polymerization (ATRP) can be advantageously used for synthesizing polyacrylate PSA, in which case as an initiator of a mono or difunctional secondary or tertiary halide And Cu, Ni, Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag or Au (EP 0 824 111 A1; EP 826 698 A1; EP 824 110 A1; EP) as initiators for halide extraction. 841 346 A1; EP 850 957 A1) may be mentioned. Various possibilities of ATRP are further described in US Pat. No. 5,945,491 A, US Pat. No. 5,854,364 A and US Pat. No. 5,789,487 A.

Orientation, Coating Process, Treatment of Carrier Material with Thermally Conductive PSA

To prepare the oriented PSA, the polymer described above is preferably coated as a hot melt system (ie from the melt). Therefore, for this production method, it is necessary to remove the solvent from the PSA. In principle, any technique known to those skilled in the art can be used. One very preferred technique is to concentrate using a single screw or twin screw extruder. The twin screw extruder can be operated with either co-rotating or counter-rotating. The solvent or water is preferably distilled through two or more vacuum steps. Moreover, reverse heating is carried out depending on the distillation temperature of the solvent. The residual solvent fraction is preferably less than 1%, more preferably less than 0.5% and very preferably less than 0.2%. The hot melt is further processed from the melt.

Orientation in the PSA is created during coating through the coating process. Different coating techniques can be used for coating as hot melt and also for orientation. In one embodiment, the thermally conductive PSA is coated by a roll coating process and the orientation is created by drawing. Various roll coating techniques are described in "Handbook of Pressure Sensitive Adhesive Technology" by Donatas Satas (van Nostrand, New York 1989). In another embodiment, the orientation is achieved by coating through the melt die. The contact process and the non-contact process can be distinguished herein. Here, the orientation of the thermally conductive PSA is produced on the one hand by die design in the coating die or else by drawing operations after exiting the die. The drawing ratio can be adjusted by, for example, the width of the die gap. Drawing takes place whenever the layer thickness of the PSA film on the carrier material to be coated is less than the width of the die gap.

In another preferred method, this orientation is achieved by extrusion coating. Extrusion coating is preferably carried out using an extrusion die. The extrusion die used has the advantages of one of three categories: T-die, fishtail die and coathanger die. Each type is different in the design of their flow channels. The shape of the extrusion die can also create specific orientations in the hot melt PSA. In addition, similar to the melt die coating, also by drawing a PSA tape film, the orientation after exiting the die can be obtained.

In order to produce oriented acrylate PSAs, it is particularly preferred to carry out the coating onto the carrier using a coating hanger die, specifically in such a way that the polymer layer is formed on the carrier by moving the die relative to the carrier. The elapsed time between coating and crosslinking is advantageously small. In one procedure, crosslinking is preferred after less than 60 minutes, more preferably less than 3 minutes in another procedure, and very preferably after less than 5 seconds in another continuous procedure.

The carrier material treated with the thermally conductive PSA may be a single sided or double sided adhesive tape.

In one embodiment, a transfer tape is produced. Examples of suitable carrier materials include all siliconized or fluorinated films with a release effect. Film materials that may be mentioned herein include, for example, BOPP, MOPP, PET, PVC, PU, PE, PE / EVA, EPDM, PP and PE. Moreover, for transfer tapes, release papers (such as glass paper, kraft paper, polyolefin coated paper) can also be used.

If the carrier material remains in the PSA (for example in the form of a carrier film), it is also preferable to use a carrier material having a high thermal conductivity. Also in this case, for example, a film containing boron nitride, aluminum oxide, silicon nitride can be used. However, it is also possible to use metal foils. Particularly preferred films consist of aluminum, copper, stainless steel, metal alloys and the like. But polysilicon is also suitable as carrier film.

The best orientation effect is obtained by depositing onto the cooling surface. As a result, during coating the carrier material must be cooled directly by the roll. The roll may be cooled by the liquid film / contact film or by the cooling gas on the outside or inside. Cooling gas may also be used to cool the PSA exiting the sheath die. In one preferred procedure the roll is wetted with the contact medium and then placed between the roll and the carrier material.

For this procedure, both melt and extrusion dies can be used. In one very preferred procedure, the roll is cooled to room temperature and in an extremely preferred procedure it is cooled to a temperature below 10 ° C. The roll must also rotate.

In a further procedure as part of the production process, moreover, a roll is used to crosslink the oriented PSA.

UV crosslinking is carried out by irradiation with shortwave ultraviolet light having a wavelength range of 200 nm to 400 nm, in particular using a high pressure or medium pressure mercury lamp at an output of 80 to 240 W / cm, depending on the UV photoinitiator used. The irradiation intensity is adjusted to the respective quantum yield of the UV photoinitiator, degree of crosslinking to be performed and degree of orientation.

Moreover, electron beams can be used to crosslink the thermally conductive and oriented PSAs. Typical irradiation devices that can be used include linear cathode systems, scanner systems, and fragmented cathode systems, where an electron accelerator is involved. A broad description of the prior art and the most important process factors are described in Skelhorne, Electron Beam Processing, in Chemistry and Technology of UV and EB formulation for Coatings, Inks and Paints, Vol. 1, 1991, SITA, London. Typical accelerator voltages are located in the range of 50 kV to 500 kV, preferably in the range of 80 kV to 300 kV. The scattering capacity used is in the range of 5 to 150 kGy, in particular in the range of 20 to 100 kGy. It is also possible to use two crosslinking methods or other methods that allow high energy irradiation.

In a further preferred manufacturing method, the thermally conductive and oriented PSA is coated onto a roll provided with a contact medium. As a result of the contact medium, the PSA can be cooled very quickly. Advantageously, it is subsequently laminated onto the carrier material. Further, as a contact medium, a material having a capacity to contact between the PSA and the roll surface, in particular, a material filling the space between the carrier material and the roll surface (not flat at the roll surface, for example, a bubble) Can be used. In order to carry out this technique, a rotary cooling roll is coated with a contact medium. In one preferred procedure, the selected contact medium is a liquid, for example water.

Examples of suitable additives for water as the contact medium include alkyl alcohols such as ethanol, propanol, butanol and hexanol and as a result of these examples are not limited to alcohol selection. Also particularly advantageous are long chain alcohols, polyglycols, ketones, amines, carboxylates, sulfonates and the like. Many of these compounds lower surface tension or increase conductivity.

Lowering the surface tension can also be achieved by adding small amounts of nonionic and / or anionic and / or cationic surfactants to the contact medium. The simplest way to achieve this is to use a commercially available washing composition or soap solution as the contact medium, preferably at a concentration of several g / l in water. In particular, suitable compounds are special surfactants which can be used even at low concentrations. Examples thereof include sulfonium surfactants (eg β-di (hydroxylalkyl) sulfonium salts) and also for example nonylphenylsulfonic acid ammonium salts or block copolymers, in particular diblocks. In particular, mention may be made of surfactants in the prior art (Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2000 Electronic Release, Wiley-VCH, Weinheim 2000).

As the contact medium, the above-mentioned liquids can be used alone or in combination with each other in each case even without addition of water. To improve salt, gel and similar viscosity to improve the properties of the contact medium (e.g., to increase shear resistance or to reduce the delivery to the inner surface of a surfactant, etc.) Additives may also be advantageously added to the contact medium and / or to the adjuvant used. In addition, the rolls may be visually smooth or have a low level surface of the structure. It has been found that the rolls have a surface structure, in particular surface roughness. This allows the wetting by the contact medium to be improved. In particular, the coating process is particularly well carried out when the roll is preferably adjustable in the range of -30 ° C to 200 ° C, very preferably in the range of 5 ° C to 25 ° C. The contact medium is preferably applied to the rolls. A second roll that absorbs the contact medium can be used for continuous wetting of the coating rolls. However, it can also be applied without contact, for example by spraying.

For variations of the manufacturing method in which the rolls are used simultaneously with, for example, electron beams, it is common to use crushed metal rolls that absorb incident electron beams and X-rays formed in the process.

To prevent corrosion, rolls are generally covered with a protective coating. The coating is preferably selected such that it is effectively wetted by the contact medium. In general, the surface is conductive. However, it may also be more advantageous to coat it with one or more coatings of insulators or semiconductor materials.

When liquid is used as the contact medium, one obvious procedure is that a second roll having a wettable or advantageously adsorbing surface must be run through a bath containing the contact medium, which roll is then wetted with the contact medium. It is applied to the film of the contact medium by being immersed or impregnated therein and contacting the roll.

In one preferred process, the PSA is directly coated and crosslinked onto the contact medium roll. For this purpose, the methods and apparatus described for UV crosslinking and EB crosslinking can then be used. The thermally conductive and oriented PSAs are then transferred to the carrier material after crosslinking. Carrier materials already mentioned can be used.

The orientation properties in thermally conductive PSAs depend on the coating process. The orientation can be controlled, for example, by the die temperature and the coating temperature and also by the molecular weight of the polymer.

The degree of orientation is freely adjustable through the die gap width. The thicker the PSA film extruded from the coating die, the greater the extent that the adhesive is drawn into a relatively thin PSA film on the carrier material. The drawing operation can be freely adjusted by the freely adjustable die width as well as the decreasing web speed of the carrier material.

The orientation of the adhesive material can further be measured by infrared dichroism or X-ray dispersion with a polarimeter. In many cases, the orientation in acrylate PSA is known to be maintained for only a few days in an uncrosslinked state. During non-operation or storage, the system slows down and loses its preferential direction. As a result of crosslinking after coating, the effect can be significantly enhanced. Relaxation of the oriented polymer chain is concentrated towards zero and the oriented PSA can be stored for a very long time without losing its preferential orientation.

In one preferred method, the degree of orientation is determined by measuring shrinkage recoverability in the glass film (see Test B).

In addition to the described method, orientation can also be produced after coating. In this case, a stretchable carrier material is then preferably used and then the PSA is drawn during stretching. In this case, it is also usually possible to use PSA coated from solution or water. In one preferred procedure, the PSA so drawn is then crosslinked with actinic radiation.

Usage

The invention further provides for the use of thermally conductive and oriented PSAs to couple components in the electrical and electronics industries. Particularly preferably, the PSA tapes of the present invention are used to couple cooling units to high temperature electrical or electronic components. The elasticity of the PSA prevents or minimizes it from leaking out of the edge in preferential orientation after bonding. This process is further accelerated by the temperature effects of the electrical / electronic components. In addition, the thermally conductive particles in the PSA are also oriented by stretching and attracted in the preferred direction. As a result of this process, the thermal conductivity in the orientation direction is lowered such that the PSA and also the corresponding PSA tapes generally have anisotropic thermal conductivity.

In a further preferred embodiment of the invention, the PSA tapes of the invention do not have any electrical conductivity.

The invention is described below by way of examples and experiments.

The following test methods were used to examine the samples:

Gel Permeation Chromatography GPC (Test A)

Average molecular weight M _W and polydispersity PD were determined by gel permeation chromatography. The eluent used was 0.1 vol% trifluoroacetic acid containing THF. Measured at 25 ° C. The preliminary column used was PSS-SDV 5μ, 10 ³ Hz, ID 8.0mm x 50mm. Columns PSS-SDV, 5μ, 10 ³ mm ³ , and also 10 ⁵ mm ³ and 10 ⁶ mm ³ with IDs of 8.0 mm × 300 mm, respectively. Sample concentration was 4 g / l and flow rate was 1.0 ml per minute. Measurements were made against PMMA standards.

Shrinkage Restoration Measurement (Test B)

Strips of at least 30 mm in width and 20 cm in length were cut parallel to the coating of the hot melt. Each of the four strips was laminated with each other with an application amount of 100 g / m ² and eight strips were laminated with each other at 50 g / m ² to obtain a comparable layer thickness. The specimen obtained in this way was then cut to exactly 20 mm in width and overstick with a space of 15 cm at each end with a paper strip. The test specimen thus prepared was suspended vertically at RT and the length change was monitored over time until no further shrinkage of the sample could be observed. The initial length, reduced by the final value, was recorded as% of shrinkage resilience relative to the initial length.

To measure orientation after a long time, the coated and oriented PSAs were stored in swatch form for a long time and then analyzed.

Measurement of thermal conductivity (test C)

Thermal conductivity was measured by the copper block method. The PSA tape under test was bonded between two copper blocks. Two temperatures were measured at a distance of 5 mm and 15 mm from the surface and extrapolated to the surface temperature. The heat sensor used was a Ni-CrNi thermocouple. The measuring device is sealed with PVC to prevent radiation loss. The heat was coupled through the electric thermal element. The measuring device was cooled down with a copper water condenser. The size of the measuring body (PSA tape) was 25 mm x 25 mm. The measurement subject was in each case a non-resilient PSA tape film. Thermal conductivity was calculated on the assumption that the heat flow density in the two blocks is the same and that the heat flow density of the PSA layer is also the same.

q _cu = q _PSA

q _cu = heat flow density in the copper block

q _PSA = heat flow density of pressure sensitive adhesive

If the heat flow density in the equation is replaced by a sentence describing heat conduction at the plate wall, this is according to the following equation:

λ _CU  Ｘ (T _One -T ₂ ) / s = λ _PSA X (T _b -T _t ) / S _sa

λ _CU = copper conductivity

λ _PSA = conductivity of pressure sensitive adhesive

s = distance between measuring points 1 and 2

S _sa = layer thickness of the sample

T ₁ , T ₂ = temperature at measuring points 1 and 2

T _b , T _t = surface temperature of the top and bottom blocks.

The equation was reconstructed to obtain thermal conductivity:

λ _PSA  = λ _CU  Ｘ S _sa (T _One -T ₂ ) / s X (T _b -T _t )

The thermal conductivity of copper was as follows: λ _CU = 372 W / mK

180 ° bond strength test (test D)

A 20 mm wide strip of acrylate PSA coated with polyester or siliconized release paper was applied to the steel plate. Depending on the direction and the drawing, specimens of longitudinal or transverse axes were bonded to the steel plate. The PSA strip was pressed twice on the substrate using a weight of 2 kg. Immediately thereafter, the adhesive tape was peeled off the substrate at 30 mm / min and 180 ° angles. The steel plate was washed twice with acetone and once with isopropanol. The measurement results were recorded in N / cm and averaged from three measured values. All measurements were performed at room temperature under controlled climatic conditions.

Thermally conductive materials used :

Hollow aluminum oxide sphere:

50 μm hollow sphere made of aluminum oxide with a thermal conductivity of 0.27 W / mk and a specific thermal resistance of 6 X 10 ¹³ Ωcm

Graphite:

Graphite KS 6 with an average particle size of 6 μm was tested. The average thermal conductivity of the material was 155 W / mk.

Sample manufacturing

Polymer 1

A conventional 200 L reactor for free radical polymerization was charged with 2400 g of acrylic acid, 64 kg of 2-ethylhexyl acrylate, 6.4 kg of N-isopropylacrylamide and 53.3 kg of acetone isopropanol (95: 5). After passing through the reactor for 45 minutes with stirring of nitrogen gas, the reactor was heated to 58 ° C. and 40 g of 2,2′-azoisobutyronitrile (AIBN) was added. The external heat bath was then heated to 75 ° C. and the reaction was kept at this external temperature. After 1 hour of reaction time, 40 g of AIBN was further added. After 5 and 10 hours, each time point was diluted to 15 kg of 15 kg of acetone / isopropanol (95: 5). After 6 and 8 hours, 100 g fractions of each dicyclohexyl peroxydicarbonate (Perkadox 16 ^® , Akzo Nobel) in a solution of 800 g of acetone were added. After 24 hours reaction time the reaction was terminated and the batch was cooled to room temperature. As a result of measuring the molecular weight by Test A, M _W was 814,000 g / mol and polydispersity M _W / M _n was 5.2.

Polymer 2

A conventional 200 L reactor for free radical polymerization was charged with 1200 g of acrylic acid, 74 kg of 2-ethylhexyl acrylate, 4.8 kg of N-isopropylacrylamide and 53.3 kg of acetone isopropanol (95: 5). After passing through the reactor for 45 minutes with stirring of nitrogen gas, the reactor was heated to 58 ° C. and 40 g of 2,2′-azoisobutyronitrile (AIBN) was added. The external heat bath was then heated to 75 ° C. and the reaction was kept at that external temperature. After 1 hour of reaction time, 40 g of AIBN was further added. After 5 and 10 hours, each time point was diluted to 15 kg of 15 kg of acetone / isopropanol (95: 5). After 6 and 8 hours, 100 g fractions of each dicyclohexyl peroxydicarbonate (Perkadox 16 ^® , Akzo Nobel) in a solution of 800 g of acetone were added. After 24 hours reaction time the reaction was terminated and the batch was cooled to room temperature. As a result of measuring the molecular weight by Test A, M _W was 801,000 g / mol and polydispersity M _W / M _n was 5.7.

Example 1:

Polymer 1 was mixed with 5% by weight graphite KS 6 based on the polymer fraction.

Example 2:

Polymer 1 was mixed with 10% by weight of KS 6 based on the polymer fraction.

Example 3:

Polymer 2 was mixed with 20% by weight hollow aluminum oxide spheres based on the polymer fraction.

Example 4:

Polymer 2 was mixed with 10% by weight of KS 6 based on the polymer fraction.

i) preparation of specimens for measuring shrinkage resilience;

PSA in solution was concentrated on a Bersdorff concentrated extruder at a throughput of about 40 kg / h at a temperature of about 115 ° C. After concentration, the residual solvent fraction was less than 0.5% by weight. The composition is then coated onto a 12 μm PET film previously coated with 1.5 g / m ² of silicone (polydimethylsiloxane) at a defined coating temperature (composition temperature) and a web speed of 10 m / min, with a die gap of 300 μm. The composition was applied through a phosphorus coated hanger extrusion die and the width of the coating was 33 cm. Set the drawing ratio to 3: 1 for a coating amount of 100 g / m ² (PSA layer about 100 μm thick) and set the drawing ratio to 6: 1 for a coating amount of 50 g / m ² (PSA layer about 50 μm thick) It was.

The siliconized PET film was passed on a rotating steel roller while cooling to 5 ° C. Thus, at the point of contact between the PSA film and the PET film, the PSA film immediately cooled. The coating amount was 50 or 100 g / m ² . In a continuous process, after about 5 m of web section, the PSA tape was then crosslinked with an electron beam.

For electron beam irradiation, crosslinking was carried out using a device from Electron Crosslinking AB, Halmstad, Sweden. The coated PSA tape was guided through the accelerator window of the accelerator onto the chill rolls present in standard form. Within their irradiation zone, atmospheric oxygen was replaced with pure nitrogen. The web speed was in each case 10 m / min. Irradiation was carried out under an acceleration voltage of 200 kV.

To measure shrinkage resilience, test B was performed.

To measure thermal conductivity, test C was performed. Bond strength was measured according to test D.

result

In a first step, two polymers were prepared having an average molecular weight M _W of about 800,000 g / mol. Examples 1 to 4 of the present invention were carried out using the PSA. As the thermally conductive material, graphite was selected on the one hand and hollow aluminum oxide spheres on the other hand.

In the first analysis, the degree of orientation of each PSA was measured. Therefore, the shrinkage recovery in the glass film in the following paragraph was measured according to test method B. The measured values are summarized in Table 1.

Consideration of Shrinkage Restoration Value Measured on Glass Films (Test B) Example Shrinkage Restoration in Glass Films (Test B) One 70% 2 72% 3 66% 4 68%

In Table 1 all the examples showed excellent elasticity. A further prerequisite for the PSA of the present invention is thermal conductivity. Therefore, below, the thermal conductivity of each Example was measured according to the test method C. The measured values are summarized in Table 2.

Consideration of thermal conductivity measured according to test C Example Thermal Conductivity in [W / mK] (Test C) One 0.1094 2 0.1603 3 0.0733 4 0.1645 Polymer 1 0.0524 Polymer 2 0.0547

All thermal conductivity was measured for a layer thickness of 50 μm. Thermal conductivity of base polymers 1 and 2 was also included. Table 2 above shows that the examples of the present invention show excellent thermal conductivity, in which case the thermal conductivity is higher than that of the base polymers 1 and 2. Thermal conductivity can be varied by adding a thermally conductive material

In order to confirm the adhesive properties, the bond strength to the steel was further measured. The layer thickness of PSA for these measurements was 50 μm. The measured values are listed in Table 3.

Consideration of bond strength measured according to test D Example  Bond Strength for Steel (Test D) [N / cm] One 3.0 2 2.7 3 2.5 4 2.6

The values shown in Table 3 above make it clear that Examples 1 to 4 exhibit pressure-sensitive adhesive properties. The amount of additives can likewise adjust the joint strength. High fraction of filler material lowers the bond strength.

Claims (16)

A method of making a pressure sensitive adhesive article having at least one thermally conductive pressure sensitive adhesive layer, the method comprising: A layer of thermally conductive pressure sensitive adhesive that is anisotropic for at least one property is produced in a coating process by stretching, drawing or pressing, And wherein the layer has a shrinkback of at least 3% relative to the longitudinal side of the layer in at least one direction along the face of the layer, measured on a free pressure-sensitive adhesive film. The method according to claim 1, wherein the coating process is a hot melt roll coating process, a melt die coating process or an extrusion coating process. The method of claim 1 wherein the coating process is a conventional coating process using subsequent stretching or drawing on a stretchable carrier. The method of claim 1, wherein the thermally conductive pressure sensitive adhesive is coated on one or both sides of the sheet or tape carrier. 5. The method of claim 4 wherein the carrier is a transfer tape, release liner or thermally conductive carrier material. The process according to claim 1, wherein the pressure sensitive adhesive used is based on polyacrylates and / or polymethacrylates. 7. The pressure sensitive adhesive according to claim 6, wherein the pressure sensitive adhesive uses at least 50% by weight of one or more acrylic monomers from the group of compounds of formula wherein the average molecular weight M _W of the pressure sensitive adhesive is at least 200,000 g / mol. Way: Where R ₁ is H or CH ₃ , The radical R ₂ is H or CH ₃ or is selected from the group of branched or straight chain, saturated alkyl groups of 2 to 30 carbon atoms. The crosslinking agent, in particular the difunctional or polyfunctional acrylate and / or methacrylate, the difunctional or polyfunctional isocyanate, or the difunctional or polyfunctional epoxide is pressure sensitive. Added to the adhesive. 9. The method of claim 8, wherein the pressure sensitive adhesive is preferably photochemically crosslinked immediately after or during the hot melt coating. 10. The thermally conductive material according to claim 1, wherein the thermally conductive material is in particular a metal or ceramic material, preferably in powder form, graphite, aluminum, aluminum oxide, aluminum nitride, titanium dioxide, titanium boride, Silicon nitride, carbon nitride or boron nitride. Process according to claim 10, characterized in that the thermally conductive material is mixed in a proportion of 5 to 200% by weight, preferably 6 to 50% by weight, based on the weight of the pressure sensitive adhesive. The method according to claim 1, wherein the thermal conductivity of the pressure sensitive adhesive is at least 0.05 W / mK. 13. The direction according to any one of the preceding claims, wherein the thermal conductivity is anisotropic and is lower along the face of this layer than across the face of the pressure-sensitive adhesive layer, and the thermal conductivity crosses the face of the layer. At 0.06 W / mk or more. The pressure sensitive adhesive of claim 1, wherein the pressure sensitive adhesive comprises an aging inhibitor, light stabilizer, ozone protectant, fatty acid, plasticizer, nucleating agent, swelling agent, accelerator and / or filler. Characterized in that it comprises additional substances or additives. A pressure sensitive adhesive article obtainable by the method according to any one of the preceding claims, in particular for joining two electrical parts. 16. The pressure sensitive adhesive article according to claim 15 in the form of a diecut.